1. Field of the Invention
The present invention relates to the high speed mixed signal integrated circuits. In particular, the present invention relates to a cost function circuit suitable for use in a pre-distorter.
2. Discussion of the Related Art
The design of a cost function circuit depends heavily on its application. Different power and die size requirements, for example, may lead to different design choices in the design of the cost function circuit. An analog cost function may be used, for example, to provide a polynomial function of a signal. Such a polynomial function may be used, for example, in a pre-distorter to implement the inverse of a channel transfer function. Typically, for use in a communication circuit (e.g., GSM with a 900 MHz carrier signal or WCDMA with a 2.0 GHz carrier signal), the bandwidth required of a cost function circuit may exceed a few hundred megahertz (MHz). In addition, unlike an implementation in a digital circuit (e.g., digital signal processor, or DSP), a mixed signal cost function generator circuit has to contend with variations due to process, variation and temperature (PVT) and other non-ideal properties. These requirements pose significant challenges to a cost function generator circuit design.